Given the rapid introduction of new types of portable electronic devices (e.g., Personal Digital Assistants, Text messaging pagers, MP3 players, cell phones), and the rapid development of novel functionality, an important objective in designing electronic devices is to provide intuitive user interfaces. Computer mouse-like keys and qwerty keyboards are some examples providing intuitive interfaces. However, these interfaces are directed more at providing input to the electronic device rather than providing content related feedback to a user. Touch screens along with graphical user interfaces (GUI) provide information to the user, but only if the user is looking at the screen.
Devices more recently are actively responding to user input by providing tactile cues or responses to the user. The vibrator in a cell phone or pager is a good example. Other examples include an input key that provides a clicking sound when moved; a key or touch screen that moves suddenly or vibrates in an opposed direction to the input; and a key that moves suddenly or vibrates perpendicular to the direction of input in response to a transducer attached to the device housing.
Morphable user interfaces are expected to be an important design consideration for the next generation of portable electronic devices. Users will find the input interface simpler and more intuitive to use because its physical appearance will match a selected function. However, the conventional means of providing tactile feedback, to a finger for example, has been mechanical dome switches which will not function well with morphable graphic user interfaces; therefore, haptics becomes a critical enabler. While DC rotary or linear vibration motors could provide tactile feedback to a finger input with an optimized driving algorithm, the buzz-like vibration profile is very different from a dome switch that generates a sharp mechanical click at the user's finger. On the other hand, a piezoelectric actuator can produce a much more realistic click sensation which can provide the operator with the illusion that a real physical key has been pressed.
One type of haptic feedback may be found, for example in U.S. Pat. No. 6,710,518. An electromechanical transducer produces an impulse of mechanical energy that propagates through a mounting boss to the entire device. This mechanism is great for providing a “call alert” for example, but does not allow for selective feedback to individual input locations (keys, buttons, arrows, etc).
Another type of haptic feedback is found, for example in U.S. Patent Publications 2006/0050059 and 2006/0052143. One or several piezoelectric actuators are placed, typically at the corners, under an input device that needs to be actuated. The input device could be a keypad or a display with touch sensitive surface. Upon application of a voltage, the piezoelectric actuators deform, either pushing or pulling the entire input device in a given direction and thus give a tactile feedback to the users' hand or finger operating at the input device. The most widely used piezoelectric actuators for this purpose are typically unimorph actuators, which are made of a piezoelectric ceramic element bonded to a metal shim, or bimorph actuators, which are made of metal shim bonded in between of two piezoelectric ceramics elements. Both unimorph and/or bimorph actuators are also referred to as benders. In a unimorph actuator, the bending motion comes from the tendency of either in-plane shrinkage or expansion of the piezoelectric ceramic element under applied electric field against the mechanical constraint from the metal shim. In the case of a bimorph actuator, the two piezoelectric ceramic elements are driven such that one shrinks while the other expands, causing the bending motion. A typical placement of the benders is to anchor the edge of a circular bender, or both ends of a stripe bender, on a base structure. The center of a circular bender, or the middle of a stripe bender which has the maximum displacement, is usually used to drive a mechanical load, as illustrated in both U.S. Patent Publications 2006/0050059 and 2006/0052143. It is noteworthy that the relatively high displacement from bending motion of a unimorph actuator or a bimorph actuator is only possible from the bonded structure of piezoelectric ceramic element(s) and metal shim. A stand alone piezoelectric ceramic could not generate such displacement.
However, the voltage required to drive piezoelectric actuators to their full materials capability is about 3.0 volts/micron. This is approximately 60.0 volts for a multilayer actuator with 20.0 micrometer layer thickness, or 200 volts for a 0.1 micrometer single layer actuator sliced from bulk piezoelectric ceramics, in which the 20.0 micrometer layer and 0.1 micrometer thick actuators are the manufacturing limit. This high voltage requirement to drive piezoelectric actuators in today's small electronic devices is undesirable at best.
Accordingly, it is desirable to provide a method of providing tactile feedback to an input device in a portable communication device. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.